Vehicle steering systems and suspension systems are comprised of a number of interconnected components. The dimensional variation of the components and the geometric variation introduced at joints can create a variation in ride steer greater than a threshold amount, thereby requiring an adjustment to correct the ride steer. “Ride steer” is the change in the toe angle of a vehicle wheel that occurs with suspension ride travel (i.e., the toe in or toe out of a wheel, from top to bottom, that occurs as the suspension system moves up and down while the vehicle travels over the road).
Automotive suspensions are designed to minimize the transmission of vertical forces into a vehicle body (suspend) while creating the lateral forces required for directional control (path following). Typical suspension linkage mechanisms are configured to tip the top of the tire inboard (change camber) as the wheel moves up to maintain a desired orientation of the tire to the road surface when the vehicle body rolls relative to the ground while cornering. Because automotive tires produce lateral forces primarily due to differences between the direction that the tire is rolling versus the direction of travel across the ground (slip angle), the suspension mechanism must also control any ride steer (toe change) when a wheel moves vertically. Ride steer is relatively sensitive to the angle of the tie rod.
The number of chassis components that are assembled to create a suspension system plus the dimensional variation of parts and the geometric variation introduced at joints can create variation in ride steer that is greater than an optimally acceptable amount.
Previous ball joints have included an externally-threaded split sleeve that screws into the knuckle steer arm. A tapered ball stud then engages a tapered inner diameter of the split sleeve to expand the sleeve, locking it to the knuckle steer arm. However, such a sleeve is not configured to adjust ride steer height, because, due to its split nature, the sleeve is only securely engaged to the knuckle steer arm at the initial assembly position. Ride steer cannot be adjusted without disassembling the split sleeve, the knuckle steer arm, and the tapered ball stud.
Some suspension systems utilize active suspension technology that minimizes vertical disturbances of the vehicle body by either pulling the tire up or pushing the tire down a controlled amount under the direction of a controller to follow road profile changes, with active (i.e., controllable) force generation components used in place of springs. With minimized vertical disturbances, lateral disturbances are more easily perceived. Additionally, because tires generate lateral forces when rolling at a slip angle to the direction of travel, active suspensions demand near zero ride steer to minimize unwanted lateral force disturbances.